1. Field
A process for synthesizing nanocrystals and a composition including nanocrystals synthesized therefrom are disclosed.
2. Description of the Related Art
Nanoparticles have drawn much attention due to the fact that unlike bulk materials, their physical characteristics (e.g., energy bandgap and melting point) may be controlled by changing the particle size. For example, a gold nanoparticle has a different melting point, color, and light emitting characteristics from those of bulk gold. Similarly, a semiconductor nanocrystal (also known as a quantum dot), a semiconductor material having a crystalline structure of a size of several nanometers, has a large surface area per unit volume. In addition, a semiconductor nanocrystal exhibits a quantum confinement effect, and thus has physicochemical characteristics different from the characteristics of the bulk material. A quantum dot may absorb light from an excitation source, and may emit energy corresponding to its energy bandgap. In the quantum dot, the energy bandgap may be adjusted by varying the size and/or the composition of the nanocrystal to obtain light emitting characteristics of high color purity. Various applications of the semiconductor nanocrystal in a display element, an energy device, a bio-light emitting element, or the like have been researched.
A semiconductor nanocrystal (i.e., a quantum dot) may be synthesized by a vapor deposition method such as metal organic chemical vapor deposition (“MOCVD”) and molecular beam epitaxy (“MBE”), or by a wet chemical method of adding a precursor to an organic solvent to grow crystals. In the wet chemical method, an organic material such as an organic solvent, and the like, is coordinated to a surface of the semiconductor crystal during the crystal growth. Thereby the organic material plays a role of a dispersing agent and controls the crystal growth. Therefore, the nanocrystals produced by the wet chemical method usually have more similar size and shape than those produced by the vapor deposition method.
Unlike the bulk material, the inherent physical characteristics (such as energy bandgap, melting point, and the like) of the nanocrystal may vary depending on the size of the nanocrystal. In particular, the fact that the electromagnetic characteristics of the nanocrystal may be finely tuned makes attractive its use in various display devices and new regeneration energy devices. The devices including nanocrystals are expected to show higher efficiency and longer product lifespan. To promote the utilization of the nanocrystals, however, it is desired to establish technologies for synthesizing high quality nanocrystals with desirable physical and chemical properties by adjusting the size, structure, shape, and uniformity of the nanocrystals.